Methods and apparatus for masking and securing communications transmissions

ABSTRACT

A secure information transmission system includes one or more transmitters and one or more receivers. The transmission waveform employed includes highly randomized, independent stochastic processes, and is secured as a separate entity from the information it carries. The signal, using novel modulation methodology reducing impulse responses, has a paucity of spectral information and may be detected, acquired and demodulated only by communicants generating the necessary receiving algorithm coefficients. The physical area of signal reception is restricted to that of each intended communicant, reception areas following movements of mobile communicants. A unique instant in time is used as basis for communications keys to the securing algorithms dynamically generated on a one-time basis and never exchanged or stored by communicants. Technology is applicable to both fixed and mobile communications and may be applied to communications systems using wireless, fiber-optic, copper, acoustic and any other man-made or naturally occurring transmission media.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 11/434,510 filed May 16, 2006, which claims priority under 35U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/681,009,entitled “Method of Masking and Securing Communications Transmissions,”filed May 16, 2005. This provisional application is hereby incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to the transmission of information byelectromagnetic, optical and, or acoustical means, and more particularlyto the security of the emission and inherently any and all informationit may transport.

BACKGROUND

Information exchange is conventionally protected by encryption of themessage itself. The carrier itself is most often left unprotected forall to see, on the assumption that the information is rendered safe fromextraction by unauthorized interceptors. Current advances in computertechnology and processing power continue to drastically shorten the timerequired to decrypt all but the most complex encoding, such that onlytime-sensitive messages with no enduring value will be safe. Complexinformation encryption schemes typically increase overhead, slowingmessage transmission. Conventionally, encryption keys must be exchangedby communicants, thus rendering the encryption more vulnerable thanever. Furthermore, the knowledge that messages are being transmittedand, or exchanged is often of value and where radio is used as thetransmission medium, the radio signature itself provides a wealth oflocation, traffic, and source information. Such signals are easilyintercepted and jammed, if desired, or used for radio location to beexploited in other ways.

SUMMARY

The invention is based on a combination of the following well knownmathematical and physical principles:

1. Auto Correlation of White Gaussian Noise

The autocorrelation of white Gaussian noise (WGN) is given by theinverse Fourier transform of the noise power spectral density WGN(f):

Ra_(WGN)(τ) = ∫_(−∞)^(∞)WGN(t) ⋅ WGN(t + τ) 𝕕t = F⁻¹{G_(WGN)(f)} = (N₀/2)δ(t)

The auto-correlation function is:Ra _(WGN)(τ) is 0 for τ≠0

Any two different samples of WGN, regardless of their close proximitywill fail to correlate due to the truly random nature of WGNG _(GWN)(f)=N ₀/2 Watts/Hertz

Cross correlation is impractical, because it is impossible to generate areference.

2. Central Limit Theorem

The probability distribution of the sum of j statistically independentrandom variables approaches Gaussian distribution as j→∞, no matter whatthe individual distribution functions may be.

The probability density function (PDF) of W=X+Y is:

f_(W)(w) = ∫_(−∞)^(∞)fx(w − y)fy(y) 𝕕y = ∫_(−∞)^(∞)fx(x)fy(w − x) 𝕕xhence:

${P_{w}(w)} = {\sum\limits_{k = {- \infty}}^{\infty}\;{{{Px}(k)}{{Py}\left( {w - k} \right)}}}$thus:f _(w)(w)=f _(x)(x)

f _(y)(y)

It follows therefore that the PDF of w=x₁+x₂ . . . x_(n) is:f _(w)(w)=f _(x1)(x ₁)

f _(x2)(x ₂)

. . .

f _(xn)(x _(n))

The product of ‘n’ unrelated pseudo-random stochastic processes (Pn)greatly decreases any deterministic aspects of the signal.

When ‘n’ sets of independently random variables are used in unison, thenumber of possible combinations and permutations of events in theresulting distribution rapidly becomes extremely large.

3. WGN Variance

WGN is an idealized process having a two sided power spectral densityequal to a constant N₀/2 for all frequencies from −∞ to ∞. The noisepower variance, as noise has a zero mean, is:

σ² = var[n(t)]∫_(−∞)^(N)(N₀/2) 𝕕f = ∞

The variance for filtered WGN is finite. Correlated with one of a set oforthonormal functions, the variance of the correlator output is:

σ² = var(n_(j)) = E{[∫_(−∞)^(∞)n(t)ψ_(j)(t) 𝕕t]²} = N₀/2

The secure waveform plus noise produces a totally noise-like correlatoroutput, in the absence of a synchronized signal reference.

4. Uncertainty Principle of Information

In accordance with the “Uncertainty Principle of Information,” a signalobserved over a limited time interval, or window, has limited spectraldefinition because “the Fourier spectrum of a wave observed over afinite interval or window, is the convolution of the true spectrum ofthe wave with the Fourier transform of the window itself” The windowT_(w) observed in FIG. 3 a has the familiar sin(x)/x from of the Fouriertransform shown in FIG. 3 b 1/T_(w). the shorter duration window, shownin FIG. 3 c transforms to a broader peak as seen in FIG. 3 d,Δf=1/T_(w). Spectral windows containing relatively few cycles containlittle spectral information, since Δf/f₀≈1.

The invention provides numerous advantages including, but not limited tothe following:

-   -   Renders signal virtually invisible to all except the intended        correspondents.    -   Secures carrier as a discrete element, as opposed to the        information it carries.    -   Signal has characteristics, blends with and becomes part of the        ambient AWGN.    -   Difficult to detect.    -   Unauthorized acquisition extremely difficult.    -   Minimizes radio signature.    -   Uses novel modulation scheme greatly reducing impulse responses.    -   Restricts area of signal reception to that of the intended        receiver.    -   Signal reception area may be restricted at will for individual        network elements.    -   Permits users to determine relative positions of other network        elements.    -   No masking algorithm keys transmitted or exchanged.    -   Unique key allocated to each communication.    -   Keys may be instantly changed at will.    -   Reverse engineering will not reveal the keys.    -   Does not interfere with or limit the use of information and, or        protocol encryption, in any way.    -   No transmission overhead.    -   Does not interfere with transmission protocols in any way.    -   Signals highly orthogonal and, or having very low level cross        correlation characteristics.    -   Enhances spectrum and bandwidth efficiency.    -   Permits use of physically co-located wireless systems using same        frequency.    -   Highly impervious to jamming and interference.    -   Applicable to both fixed and mobile communications.    -   May be used to overlay and secure networks and systems employing        IEEE Standard 802.11.    -   May be used to secure CDMA systems.    -   May be applied to communications systems using wireless,        free-space optical, fiber optics, copper, acoustical and other        man-made or natural transmission media.    -   Uses novel phase shift keying modulation methodology resulting        in drastically reduced impulse response.    -   Invention embodiment may be realized using inexpensive hardware.    -   Embodiment may use commercial/industrial grade master timing        oscillators.    -   Embodiment may be realized using commercial off-the-shelf (COTS)        components including field programmable gate arrays (FPGA's), no        proprietary components are necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a conventional DS-SS radio link.

FIG. 2 illustrates a spectral comparison of a peaked signal and aconventional DS-SS signal.

FIGS. 3 a-3 d shows an application of the Uncertainty Principle ofInformation.

FIG. 4 shows a simplified arrangement of a DS-SS transmitter andreceiver employing a variable frequency PN spreading sequence.

FIG. 5 shows how a signal is spread by a PN with varying chip and dwellrate.

FIGS. 6 a-6 f show the spectral results of two conventional digitallymodulated radio signals, peaked signal and DS-SS, and the RF signalenvelope resulting from an exemplary embodiment of the invention.

FIG. 7 a shows a more detailed view of the example in FIG. 6F. FIG. 7 bshows spikes resulting from the chip-clock frequency change impulseresponse occurring at random intervals.

FIG. 8 illustrates an example of a sub-system embodiment of chipvariations, chip frequency, chip-dwell, and chips-per-symbol employingconventional analog modulation methodology.

FIG. 9 illustrates an example of a transmitter embodying PN chip-clockvariations, pseudo-randomly varied data symbol rate, and pseudo-randomlyvaried RF carrier.

FIG. 10 shows an example of a receiver arrangement to work with thetransmitter shown in FIG. 9.

FIG. 11 shows conventional m-ary phase shift keying of π radians wherethe initial signal phase is reversed resulting in two sequential halfcycles of similar phase.

FIG. 12 shows a conventional m-ary phase shift keyed signal shifted −π/2or +3π/2 radians and the resulting shifted signal.

FIG. 13 shows a conventional m-ary phase shift keyed signal shifted +π/2or −3π/2 radians and the resulting shifted signal.

FIGS. 14-16 illustrate a minimum impulse phase shift keying (MIPSK)technique.

FIG. 17 illustrates a flowchart showing the basic principle ofinitialization in accordance with an exemplary embodiment of theinvention.

FIG. 18 shows an elapsed time from a Com-Root and its division intoCTP's and OTP's

FIG. 19 illustrates the basic methodology employed in an exemplaryembodiment of the invention, including the signal transmission timerelationship between a radio transmitter and receiver, assuming directline-of-sight communication, with no multi-path signals.

FIG. 20 illustrates identification of a time instant for establishmentof a Com Key by selecting a specific data symbol transition within agroup of symbols as it transits a predetermined point within thetransmitter.

FIG. 21 shows a flowchart of the Com-Key establishment in accordancewith an exemplary embodiment of the invention.

FIG. 22 illustrates an example of one method of setting up Com-Keys fromone end of a communications link only

FIG. 23 shows an example of how a synchronization window may bedetermined for equipment using drifting master timing oscillators andoperating in the absence of time-reference synchronization.

FIG. 24 illustrates a further flow chart showing the basic principle ofinitialization taking master timing oscillator drift into account.

FIG. 25 shows an example of restricted communicant operability zonescreated by emission from an omni-directional emitter.

FIG. 26 is a linear representation of areas of Com-Key validity as afunction of distance and time for Com-Keys generated at one microsecondintervals.

FIG. 27 illustrates an exemplary embodiment with an infrastructure typenetwork comprising a base station, or access point, with remotestations, mobile or fixed.

FIG. 28 shows an example of an arrangement wherein the mobile stationsare able to move freely and adjust the Com Key timing to compensate fordeviations from the initial set-up location.

FIG. 29 illustrates an exemplary embodiment in which the technologyresulting from the present invention can be used to advantage in ad-hocnetworks and other more complex arrangements.

DETAILED DESCRIPTION

Embodiments of the invention are described below in the context ofdirect sequence spread spectrum (DS-SS) radio equipment and systems.However, it will be readily apparent to those well versed in the art,that the present invention and embodiment details described herein areapplicable to virtually any type of information transmission systemsusing, but not limited to, wireless, free-space optical, fiber optics,copper, acoustical and other transmission media. Thus the presentinvention shall not be construed as limited in any way to specificexamples provided herein.

Conventional DS-SS radio transmissions, while lower in instantaneousspectral power density than equivalent peaked signal transmissions andoften immersed in the AWGN, are still easily detectable by virtue of theadditive characteristic of white Gaussian noise showing increased powerspectral density in the signal's location coupled with deterministic andcyclostationary features of the signal. These same features enable awould-be interceptor to gather and assemble information sufficient todetermine the parameters of the signal and location of the emitter, thuspermitting signal acquisition and, or effective jamming. Furthermore, inconventional communications it is necessary for encryption keys used toestablish pseudo-random noise, PN, sequences and other variableparameters to be exchanged over the air, or stored in memory in theequipment.

The present invention establishes the necessary unique signal parameteralgorithm coefficients without exchange of keys and significantlyreduces or eliminates each of the deterministic and cyclostationaryfeatures replacing them by a combination of non-repetitive, unrelated,dynamically programmable stochastic processes. More specifically itcreates a unique randomly varying waveform for each transmission,thereby increasing the difficulty of signal detection, unauthorizedacquisition and exploitation.

The main deterministic and cyclostationary features of a conventionalDS-SS are:

1) Carrier a) Constant spectral profile b) Strictly band limited c) Banddefined d) Well defined signature 2) Data Symbol Rate a) Predeterminedunvarying rate, repetitive symbol duration 3) Chip Rate a) Predeterminedunvarying rate. b) PN symbols create cyclostationary modulation featuresin combination with deterministic data symbol rate. 4) PN -Pseudo-Random-Noise Spreading Code a) The PN sequence becomes repetitivein most applications b) Easily detected. c) Sequence can be compiled byan unauthorized interceptor.

All the foregoing features facilitate compilation of information, basedon which, it is possible to determine the transmission signal parametersthereby enabling its acquisition.

FIG. 1 is a simplified diagram of a conventional DS-SS radio linkcomprising a transmitter 101 and a receiver 106. The data input 104modulates the transmitter carrier frequency, which in turn is furthermodulated, to spread the signal, by a pseudo-random noise sequence 102,clocked at a constant frequency by a chip clock 103, operating at ahigher periodic rate than that of the data input 104. The resultingconventional spread signal is transmitted to the receiver in which thesignal is de-spread and the data 110, retrieved by a reversal of thetransmit process using well established methods. A spectral comparisonof a peaked signal 201, and a conventional DS-SS signal 202, is shown inFIG. 2.

In the present invention the main deterministic and cyclostationaryfeatures of a conventional DS-SS enumerated above are reduced or removedby introduction of a series of independent, unrelated, random stochasticvariations applied to the prerequisite equipment subsystem functions.All variations and sequences are independent of each other and uniquefor all variables. As previously stated, one of the key objectives ofthis invention is to radically increase the difficulty of exploitationof the waveform and the information carried by it. The inventiondrastically reduces the RF signature both in instantaneous magnitude andrecognizable profile in conjunction with which it reduces individualwaveform component spectral information below the level required forre-compilation of the waveform without the use of an accurate temporallysynchronized reference signal. FIG. 3 shows the application of theUncertainty Principle of Information as mentioned in the foregoing. Itshould be noted that the drawings in FIG. 3 are not to scale andtemporal and spectral windows are purposely disproportionate for ease ofexplanation. FIG. 3 a shows a time window T_(w), 302, of a sinusoidalsequence 301. The Fourier transform of the waveform 301 gives thefamiliar sin(x)/x spectral representation in FIG. 3 b. The transformedwindow 1/T_(w) is represented by the main lobe 305, while the singlecycle 1/f₀, 303, appears as the peak, 304. When the window 302, isshortened, as shown in FIG. 3 c, 307, making the time of observationmore precise, its transform spectrally blurs, as seen in FIG. 3 d. Itwill be seen, therefore, that the spectral information alone containedin FIG. 3 d is insufficient to determine its exact frequency. The lackof spectral information present in the waveform invention describedherein, therefore greatly increases the difficulty of reconstructing thewaveform when presented only with spectral information. The accuratetiming information contained in a reference signal will enable completerecognition and placement of the representative spectral code elements.As stated in the foregoing, when ‘n’ sets of independently randomvariables are used in unison, the number of possible combinations andpermutations of events in the resulting distribution rapidly becomesextremely large. In the following invention embodiment example, sevenunrelated, random stochastic sequences are used, each containing a largenumber of random events. It will be readily seen by persons familiarwith both the art and the underlying theory that the number ofcombinations and permutations tends to become astronomical, therefore,without sufficient spectral and temporal information it becomes almostimpossible to extract the necessary information to reconstruct any ofthe component sequences sufficiently to retrieve the transmitted data.

In the following example of an embodiment of the invention, sevenindependent pseudo-random variable stochastic processes with independentdistributions are employed. Pseudo-random variations are applied to thefollowing:

Long, unique, PN spreading sequences, on a one-time use basis.

Chip clock frequency.

Chip frequency-dwell period.

Data symbol rate.

Data symbol rate dwell.

RF carrier frequency (dithering).

Carrier frequency dwell-time.

A number of other variations are also possible, for example, including,but not limited to:

-   -   Separate PN codes for the in-phase (I) real, part of the complex        signal and the quadrature (Q) imaginary, part.    -   Carrier phase dithering.    -   Multiple tandem PN modulation stages each with individual        variations. Carrier amplitude adjustment.

The number of variations applied to waveform generation was severelylimited in prior art due to the inability of communicants tosynchronize. Communication using a waveform comprised of a combinationof numerous independent stochastic components is facilitated, in thisinvention, by its ability to synchronize when employing other thanhighly accurate timing devices.

Long unique PN sequences for use on a one-time basis only may begenerated in a multiplicity of ways, using well known shift registermethodology, for example, or by other more secure cryptographicalgorithms. The use of a PN sequence longer than any singlecommunication period significantly increases the difficulty ofassembling the complete sequence required for dispreading the signal.Using the sequence on a one-time only basis denies the would-beunauthorized interceptor the any advantage of information gleaned fromprior intercept attempts. Furthermore, the non-repetitive nature of thesignal prevents even occasional spectral lines in signal analysis.

It will immediately be apparent to those familiar with the art that thePN and chip-clock rate may be varied in several ways, for example, butnot limited to:

Varying chip-clock frequency and dwell times applied to directly to thePN spreading sequence, with total chips per symbol as an integer.

Varying chip-clock frequency and dwell times applied to directly to thePN spreading sequence, where the total chips per data symbol is notnecessarily an integer.

Varying chip-clock frequency and dwell times with random clock phasechanges independent of data symbol transition positioning.

Varying chip-clock frequency and dwell times with random clock phasechanges, some of which are timed to coincide with potential data symboltransition timing.

A combination of two, or more, unrelated PNs are used to spread thesignal.

A combination of two, or more, unrelated PNs with coincident variations.

A combination of two, or more, unrelated PNs with unrelated variations.

A combination of two, or more, unrelated PNs applied to both I and Q areused to spread the signal.

Combinations of any and all of the above variation methods.

The number of chips per symbol will automatically vary as the chip-clockfrequency is varied. However, further pseudo-random variations of thenumber of chips per symbol may be either factored into the randomizationof the chip-clock variations or applied as a separate unrelatedvariable. FIG. 4 shows a simplified arrangement of a DS-SS transmitter401 and receiver 407 employing a variable frequency PN spreadingsequence. The information to be transmitted is represented by a datastream, Data In, 405, which modulates the transmitter carrier. Thetransmitter carrier is further modulated by the PN sequence, produced bythe PN generator 402, which is clocked by the variable frequencyoscillator Chip Clock 403, the frequency of which is varied inaccordance with a control sequence generated by the Shift Sequencer,404. The receiver, 407, de-spreads the received signal by applying aprecisely synchronized copy of the transmitted PN. The signal is thusrestored, and the data 412 is retrieved by demodulating the carrier inthe normal manner. In order to achieve this, a control sequence, similarto that generated by the transmitter Shift Sequencer 404, is generatedby the Shift Sequencer 410, and applied to the Chip Clock 409, toproduce a series of chip frequency variations identical to those outputby the transmitter Chip Clock 403. The timing of the receive shiftsequence is delayed to accommodate the signal transmission delay betweenthe Transmitter Antenna 406 and the Receiver Antenna 411, plus theprocessing delays of both equipments. Equipment delays and free-spacetransmission delay are calculated, as is later explained more fully, toenable exact synchronism of transmit and receive processes. The outputof the Chip Clock 409, is applied to the PN Generator 408, so that asimilar varying PN to that of the transmitter is applied in synchronismto the received signal to perform the necessary de-spreading. Basictiming synchronization between transmitter and receiver may be achievedin numerous w ways; one such method is to derive timing from receivedGPS signals. Timing synchronization signals, 413 and 414 are applied tothe transmitter and receiver Shift Sequencers, 404 and 410, Chip Clocks,403 and 409, and to the PN Generators, 402 and 408. Other methods ofsynchronization, for example include, but are not limited to, use ofother high accuracy timing sources such as standard time transmissionsfrom WWV, use of temporary field time standard equipment, portablecesium and rubidium atomic clocks, amongst a myriad of others which willbe immediately apparent to others familiar with the art. In thisinvention, synchronization is achieved without GPS or other highaccuracy timing assistance, as will be fully explained in a latersection herein.

FIG. 5 shows how the signal is spread by a PN with a varying chip rate.The signal is spread by the varying PN modulating the two data symbols501, resulting in a combination of frequency variations of the spreadsignal, 502. The period for which the chip rate frequency remainsconstant is called the dwell-time. The dwell-time for any one PN chipfrequency is pseudo-random, such that it is not deterministic and willnot produce cyclostationary features in the output signal. A number ofvarying PN chip clock frequencies with pseudo-random dwell-times 503,are shown during the two data symbol duration spread signal sequence,502. Three specific frequency variations and dwell times, 504, 505 and506, are shown with related varying chip clock timing 508, 509 and 510,in chip clock sequence 507.

The spectral results of two conventional digitally modulated radiosignals, peaked signal and DS-SS, plus the RF signal envelope resultingfrom this embodiment of the invention, are shown in FIG. 6. The datainput 601, with symbol 602, to a conventional peaked radio signaltransmitter is shown in FIG. 6A, with the resulting spectral responseportrayed in FIG. 6B. The signal is characterized by a narrow bandwidthmain lobe 604, with high amplitude, the total average power 603, beingcontained therein. The spread signal using a PN applied at a steady,unvarying, chip rate, 606, in FIG. 6C, produces the familiarconventional DS-SS RF envelope shown in FIG. 6D. The same total averagepower, 608, as the signal in FIG. 6B is now contained in a much widerbandwidth main lobe with correspondingly lower amplitude, 607.Side-lobes, 609, are also further suppressed, compared to thecorresponding spectral features, 605, in FIG. 6B.

In this embodiment example of the present invention, the symbols, 610,in FIG. 6E, are spread by a PN sequence (not shown) using a number ofpseudo-randomly varying chip-clock frequencies, and dwell times, 613 and614, as described in the foregoing, producing the frequency varyingsequences, 611 and 612, corresponding to the two symbols. The resultingRF envelope is shown in FIG. 6F. The amplitude, 615, is much less than607, in FIG. 6D, but the total average power, 616, is the same, withproportionally differing and continuously varying spectral occupancy, asevidenced by the position of the secondary lobes, 617. FIG. 7A shows amore detailed view of the example in FIG. 6F. The amplitude of the mainlobe, 701, 702, varies according to the amount of spreading resultingfrom the particular chip-clock frequency and PN—symbol product duringeach dwell period. As the spreading, 703, momentarily increases, theamplitude, 701, will drop to 702, with the total average power remainingconstant. The AWGN, 704, in FIG. 7B is shown at constant amplitude forillustrative purposes only with the spikes, 705, resulting from thechip-clock frequency change impulse response, occurring at randomintervals. In the case of real AWGN characterized by random amplitudevariations, these impulses will blend into and become part of it. Itwill be readily apparent to those familiar with the art that variationsindependent of, but similar to the foregoing chip variations, applied tothe data symbol sequence will, in turn, further randomize the signalspread to facilitate the AWGN characterization.

Carrier dithering, comprising short-term random frequency shift, withrandomized short term dwell periods serves to flatten the overallspectral response, such that the usual collection of greater amplituderesponses do not tend to centralize, or clump, thus further decreasingthe RF signature and blending the signal with the AWGN. Optimum resultsare obtained with randomization that does not produce a centerfrequency, thus, randomizing the spectral response to remove all banddefinition and thereby greatly decreasing signature characteristicswhich may act as discriminators aiding identification of the increase inpower spectral density as a signal as compared to normal random noiseperturbations.

FIG. 8 is an example of a sub-system embodiment of chip variations, chipfrequency, 806, chip-dwell, 807 and chips-per-symbol, 808, described inthe foregoing, employing conventional analog modulation methodology. Asequence of Data Symbols, 801, is modulated by a varying PN, 802, bymeans of the I and Q modulators, 803, producing a spread signal, 804.The unique variation sequence produced by the waveform algorithmcontroller, 813, is generated with coefficients provided by a keyoriginating sequence, described later in this filing. The waveformalgorithm controller generates an ongoing non-repetitive, uniquesequence of variation instructions, 806, 807 and 808, which are fed tothe shift sequencer, 805. Two, or more digitally controlled oscillators(DCO's), 809 and 810, operate sequentially. One DCO provides the currentchip frequency to the PN generator, 812, via the switch, 811, while thesecond and successive DCO's are preset and rendered operative, but notconnected, in readiness for changing to the next chip frequency, 806, onexpiry of the current dwell period, 807. By this method, the chipfrequency can be changed instantly, with no stewing and with apredetermined phase relationship, thus rendering a random changeimpervious to phase-lock tracking by a would-be interceptor. Thewaveform algorithm controller provides the necessary coefficients andalgorithmic instructions to the PN generator so that a unique sequenceis generated for each communication. The algorithm controller, inconjunction with timing derived from the master frequency control, 814,controls the precise instant the switch, 811, changes to the next DCO.Master frequency control timing is used as a basis for all sub-systems,shift sequencer, DCO's, switch and PN generator, so that each operationis fully synchronized to the necessary degree of accuracy, for example,sub-nanosecond, if required.

From time-to-time the master frequency control timing is updated andprecisely set by timing synchronization, 815, derived from GPS or otheraccurate timing source. In an embodiment of the invention where GPS isused, as one example, a GPS receiver is incorporated as part of theequipment, other embodiments may include a tunable receiver or onepre-tuned to WWV or other designated reference, for example, asmentioned in the foregoing. The GPS timing signal is accessed fromtime-to-time to correct any drift that may have occurred in thefrequency and transitions of the master frequency control oscillator andto update and correct any time-keeping error including the precisetime-of-day. Access will be in accordance with the stability of themaster frequency control oscillator and the timing accuracy required forthe operation of the equipment in the system in which it is deployed. Asmentioned above, timing synchronization signals may be derived fromalternate sources as may be deemed necessary. As will be explained indetail later, in this invention, precise timing synchronization may bederived from a communicant's signal, both for key synchronization andfor the duration of a communication. By this means, essential real-timesynchronization can be initiated and maintained in the absence ofimmediate GPS or other timing reference source.

FIG. 9 is an example of a transmitter embodying the PN chip-clockvariations described in the foregoing, pseudo-randomly varied datasymbol rate and pseudo-randomly varied RF carrier. An information streamcomprising data symbols, 901, is connected to a first-in-first-out(FIFO) buffer, 902. The output of the FIFO, which is clocked at varyingrates for periods of time determined by the waveform algorithmcontroller, 923, is fed into the I and Q separator, 903. These clockvariations are applied to the FIFO via the sub-system comprising thesequencer, 907, two or more DCO's, 908 and 909, and the switch, 910,which controls the selection of the DCO generated clock signal to boththe FIFO and the shift register, 903. The output of the shift register,903, is connected to one input of the I and Q modulators, 904, the otherinput being taken from the output of the PN generator, 917. Theoperation and configuration of the sub-system producing thepseudo-randomly dithered PN is similar to that shown in FIG. 8, whereinthe waveform sequence information is produced by the waveform algorithmgenerator, 923, and passed to the sequencer, 913, and PN generator, 917.Two or more DCO's, 914 and 915, one providing the current PN clocktiming whilst the others are preset to subsequent frequencies with thecorrect phase relationship, as may be necessary, and are routed to thePN generator when selected by the switch, 916. The output of themodulators, 904, is connected to the input of the final modulator stage,905, in this example of an embodiment of the invention. The other inputto 905 is the RF carrier. The RF carrier is generated by one of the twoor more DCO's, 919 and 920. The carrier frequency is varied on apseudo-random basis in accordance with information produced by thewaveform algorithm generator, 923, and processed by the sequencer, 918.As in previous sub-systems in this arrangement, the output of the DCO'providing the current frequency is routed via the switch, 921, to theinput of the modulator, 905, subsequent carrier frequencies being routedto the modulator, as required after appropriate dwell times. The RFcarrier is spread by the randomly varying output of modulator, 904, andcoupled to the RF Output, 906. Power amplifying and filter stages, whichmay be employed as required, are not shown for the sake of clarity.Accurate timing is provided to elements of the sub-systems by the masterfrequency control, 925, which obtains synchronization from a GPS orother accurate timing source, as described in the foregoing.

FIG. 10 shows an example of a receiver arrangement to work with thetransmitter shown in FIG. 9. As may be seen, the receiver has a similararrangement of sub-systems for decoding the variations in the signalproduced by the transmitter in FIG. 9. The RF signal input, 1001, is fedto the down converter I and Q, 1002. A sub-system comprising VariationSequencer 1009, two or more DCO's 1010 and 1011, operating similarly toDCO's 908 and 909 in FIG. 9, and the Switch 1012, generate the localoscillator frequency, in cosine and sine relationship, required for downconversion of the signal. The local oscillator frequency corresponds tothat used by the transmitter in FIG. 9, both in frequency and timing,such that the output of the down converter, 1002, will replicate theoutput of the modulator, 904, in FIG. 9, i.e. the intermediate frequency(IF), an exact replica of the IF in FIG. 9, prior to up conversion andaddition of carrier dithering variations. In order to achieve this, thewaveform algorithm controller, 1027, generates control signals inprecise synchronism with the signal received from the transmitter,inclusive of transmission and equipment delays. Thus when the localoscillator DCO, 1010 or 1011 output is selected by the switch, 1012 andapplied to the demodulator for the precise dwell time applied by thetransmitter, the output of the demodulator will correspond exactly tothe output produced by the modulator 904, in FIG. 9, when the signal wasgenerated. As synchronization variations may occur, typically due totransmission delay related signal time of arrival, (TOA), and frequencyvariation due to Doppler effect, where communicants are mobile,corresponding corrections need to be made in generation of signals bythe DCO's, 1010 and 1011. Multiple correlators, 1013, provide timing andfrequency windows, which track all received signal deviations from theparameters calculated by the sequencer, 1009. A number of correlatorarrangements can be used to provide tracking and correction signals,such as various RAKE receiver configurations, for example and othercommonly used sliding window configurations. Error signals, 1014 are fedback to the sequencer which corrects the outputs of the DCO's, 1010 and1011, so that exact synchronism is achieved and dynamically maintained.

The sub-system comprising, Variation Sequencer 1015, DCO's 1016 and1017, Switch 1018 and the PN generator 1019, generates an identicalvarying PN to that used by the transmitter in FIG. 9. Similarly to thesub-system generating the local oscillator frequency, described in theforegoing, appropriate transmission and equipment delays are calculatedby the Waveform Algorithm Controller 1027, converted to specificsub-system element commands by the Sequencer 1015, and applied to the PNsignal generated by this sub-system. The resulting replica of theoriginal PN used by the transmitter is then input to Demodulator, 1003,the output of which is converted to a digital signal by the D/A, 1004.Those familiar with the art will readily recognize that filtering, notshown for the sake of clarity, removes all higher order products fromthe signal, after which, if the sub-system is fully synchronized, itreplicates the varying rate data symbol stream present at the input tothe modulator, 904, in FIG. 9. As in the previous stage of the receiver,multiple Correlators 1005, operating in a similar manner to Correlators1013 window the filtered signal for timing errors. The error signal,1020, is fed back to the Sequencer 1015, which applies any correctionsnecessary to the DCO's 1016 and 1017.

The filtered output signal from the low pass filter is passed to theFIFO, 1006, which acts as an elastic buffer for the varying rate symbolstream. The Sequencer, 1021, DCO's, 1022 and 1023, and the switch, 1024,form the sub-system which applies a replica of the time-varyingdata-symbol clock signal, used by the transmitter in FIG. 9, to theShift Register, 1008. Provided that the SR clock output from the switchis fully synchronized, the symbol stream will be accurately recoveredand output at a constant rate. The Correlators, 1025, window the output,1008, for timing errors, for which a corresponding signal, 1026, is fedback to the Sequencer, 1021 which generates the necessary synchronizingcorrections for the DCO's, 1022 and 1023.

The master frequency control, 1028, obtains timing synchronization fromeither the GPS timing signal or other accurate source periodically, insimilar manner to the transmitter, as explained in the foregoing. Thewaveform algorithm controller formulates the necessary commandparameters for the sub-system sequencers based on the coefficientsderived from a unique communications key.

FIGS. 8, 9 and 10 and the foregoing explanation are only one example ofnumerous possible embodiments of the invention. It will be seen, bythose familiar with the art, that the various sub-systems described inthe foregoing may be realized by a wide range of combinations of digitaland analog circuitry and methodology. The invention inherently lendsitself to digital realization by virtue of the sub-system timingelements. For example, the complete transmitter system may be realizedentirely digitally, prior to a final D/A converter to convert thedigitally constructed waveform to analog form for power amplificationand antenna coupling. Similarly, the receiver may be digitally realizedfollowing antenna coupling, low noise amplification and A/D conversion.Analog down conversion will not be necessary where directly receivedsignal A/D conversion provides high enough sample rates for accuratesynchronization and demodulation. It follows, therefore, that thetechnology may be placed on a chip, FPGA, gate array or mixed signaltechnology according to the design. This in turn provides strict timingcontrol for all elements, to a degree unattainable with hitherto usedprinted circuit board and other multi-component approaches. It will alsobe seen that the technology offers a wide range of operationalflexibility. For example, various degrees of security can be dynamicallyachieved by addition or removal of particular variations from thewaveform algorithm. This can be achieved as a user function during orprior to communication, and, or as part of the resident operating systemto enable automatic communication at set levels of security with certaingroups of equipment using the waveform or to enable communication withlegacy equipment, for example.

Minimum Impulse Phase Shift Keying

Phase Shift Keying (PSK) in all of its conventional forms causessignificant impulse responses to the almost instantaneous signal phasechange, regardless of how small. These sudden phase changes causeimpulses, Dirac delta function responses which have high spectralvisibility. Therefore, if PSK is used as a means of modulation for oneor more of the variations the sudden phase change will cause an impulseresponse, which is spectrally detectable.

FIGS. 11, 12 and 13 show the three examples of basic phase transitionsin typical conventional quadriphase shift keying, QPSK, modulation. FIG.11 shows a phase shift of π radians where the initial signal phase,1101, is reversed resulting in two sequential half cycles of similarphase, 1102. The resulting signal, 1103, is phase shifted π radianscompared to 1101. FIG. 12 shows a signal, 1201, shifted −π/2 or +3π/2radians at 1202, with the resulting signal phase 1203. FIG. 13 shows asignal, 1301, shifted +π/2 or −3π/2 radians at 1302, and the resultingshifted signal, 1303. A series of other similarly radical phase shiftsignal distortions are created for other PSK modulation schemes such as,but not limited to, binary phase shift keying (BPSK), quaternary phaseshift keying (QPSK), offset QPSK (OQPSK) and other multiple phase shiftkeying (M-ary PSK) methods.

FIGS. 14, 15 and 16 show a novel method, minimum impulse phase shiftkeying (MIPSK), of performing phase shifting by insertion of a halfcycle of a frequency differing from that of the original signal suchthat the following signal waveform changes in phase from that of theprior signal whilst maintaining the original frequency. Thus, by thismethod, the signal phase is changed within the range 0 to 2π withoutvarying the frequency of the original signal for a period greater than πradians by advancing or retarding the phase. In FIG. 14 a constantfrequency signal, 1401, is phase shifted π radians commencing at thezero crossing 1402. A sinusoidal half cycle of half the original signalfrequency, 1403, is inserted into the sequence, followed by a continuoussequence of waves, 1405, at the original frequency. A dotted line, 1404,shows the conventional phase shift of π radians. FIG. 15 shows a phaseshift of −π/2 or +3π/2 radians. The signal, 1501, is phase shifted at1502, by insertion of a sinusoidal half cycle, 1503, of 3/2 times theoriginal frequency, which results in a phase shift of −π/2 or +3π/2radians. The phase shift is followed by a continuous sequence of waves,1505 at the original frequency and shifted phase. The signal, 1601, inFIG. 16 is phase shifted, in this example, by insertion of a sinusoidalhalf cycle, 1602, of ⅔ times the frequency of the original signal, whichresults in a phase shift of +π/2 or −3/2π radians. The transition isfollowed by a continuous sequence of waves of constant frequency andcorrectly shifted phase, 1604. The conventional PSK phase shift of +π/2or −3/2π radians is shown by the dotted line, 1603.

To those familiar with the art, it will be seen that M-ary phaseshifting can be accomplished by inserting half waves of various sizesvarying in duration, i.e. in frequency, from the original signalproportional to the desired phase shift. Phase shifting of this naturecan also be accomplished by use of single half cycles or combinations ofmultiple half cycles of proportionally greater or smaller duration thanwhen a single half cycle is employed. It is not necessary that all thehalf cycles in such combinations be of equal duration, only that thecumulative duration of the combination of half cycles be of theappropriate length to produce the correct phase shift. MIPSK is alsoused to apply the frequency variations in this invention for thewaveform carrier frequency dithering, so that impulse responsesresulting from instantaneous frequency change are minimized.

The number of half cycles, or combinations thereof, may be varied on apseudo-random basis to add yet a further variable to the encryptedwaveform which in itself will create DFT frequency components of lesseramplitude.

Equipment Initialization

In this invention, a unique one-time set of waveform algorithmcoefficients is generated by communicants for the duration of acommunication session, or part thereof. No keys are stored in theequipment, at other locations at any time, or exchanged prior to, orduring communications. Algorithm coefficient keys are locally generatedby equipment units at the time of communication origination and againduring the communication period itself, if required.

A precise instant in time is identified, using GPS or other timing andtime reference accurate commensurate with the timing precision requiredfor mutual operation of the particular group of equipments beinginitialized. Precise time-of-day is one method providing mutualidentification of a specific instant in time. Two or more equipments areset up such that a particular instant in time may be mutually identifiedand simultaneously stored by all as their “Com-Root”. The object of thisis to provide a point of reference in time after which it is possible togenerate sets of coefficients for the waveform generation algorithm atspecific time intervals. The set of unique waveform coefficientsgenerated at a time point selected after the establishment of theCom-Root is called a Com-Key. Com-Keys can be generated at intervalsbased on a common time base established at initialization to enablegroups of equipment to communicate with each other.

A flow chart showing the basic principle of initialization is shown inFIG. 17. For this example, it is assumed that all master timingoscillators are drift-free and therefore all equipment units haveexactly the same time. The equipment units that will be used tocommunicate with each other are connected, 1701, to an initializationcontroller which steps the units through each phase of initialization inconcert. The connection setup is such that all delays between thecontroller commands and the equipment response thereto are the same forall units within limits that will ensure that the same time instant isdetected and stored by all. The lowest master clock-rate, or otherlimiting timing factor is determined for the units, 1702. This will bethe limiting factor to determine the smallest time interval at which newwaveform coefficient keys, Com-Keys, may be generated for mutualoperation. The master clock rate and, or other information fordetermining the key generation interval, may be obtained in a number ofdifferent ways, such as, but not limited to, may be stored in equipmentfirmware, derived algorithmically or entered manually, for example. Allunits access GPS, or other time standard, and synchronize, 1703.Following time synchronization of all units, a set of initializationsymbols is assembled by the controller within which a specifictransition will be used by all to set the Com-Root. The controller thentransmits the symbol sequence to all units simultaneously. All unitswill acquire the transition at the same time and register this andrecord the precise time-of-day as the Com-Root, 1704. As the controllerdid not predetermine the time instant, the Com-Root generation is trulyrandom and anonymous. The units are now disconnected, 1705, and continueto track elapsed time, 1706.

The Com-Root can be established, 1704, in a number of different waysother than described above including, but not limited to:

1. Randomly selected anonymous instant by the controller as: a) Nearestpresent time instant b) Random past time instant c) Random future timeinstant d) Random past time instant within a specific time window e)Random future time instant within a specific time window 2. Specifictime instants selected automatically by the controller in accordancewith a preset procedure or algorithm and passed to the units forinitialization instead of by individual unit detection , as described inthe foregoing: a) Present time instant b) Specific prior time instant c)Specific future time instant 3. Dual or multiple time instants for useas operational windows during which the equipments can communicate orremain dormant. There can be an odd or even number of such instants tocreate specific time windows with the final window remaining open, asone example. 4. All of the above, inclusive of other possible timeinstant selections envisioned and or extrapolated from the foregoing,but not included for the sake of brevity and clarity, plus anycombination thereof, may be used as a Corn-Root(s) in conjunction withgeo- spatial coordinates and other geo- location information toactivate, de-activate and or control the unit's communicationcapabilities. 5. Similarly, the Corn-Root(s) may be used in combinationwith other data such as, but not limited to movement and, or lackthereof, velocity, acceleration, deceleration, bio-medical andinformation, to activate, de- activate and or control the unit'scommunication capabilities.

FIG. 18 shows the elapsed time, 1802, from the Com-Root, 1801. The timebase in this example has 1 μS interval timing; these are referred to asordinal timing points, (OTP), 1803. The elapsed time is also dividedinto larger units of time, multiple OTP's, referred to as cardinaltiming points, (CTP), 1804

It will be seen, by those versed in the art, that Com-Roots can bestored or changed in individual equipment, at any time by storing aparticular time instant to be shared by others, by manually entering adigital sequence representing the time instant, or by electricallyimplanting it, by use of recorded media or numerous other methods whichcan easily be extrapolated from the foregoing. Anonymous Com-Roots mayalso be used in this manner.

Establishing Com Keys

In the present invention, the Com Keys generated for each equipment, foreach communication session, are unique. There are many bases ofgeneration for unique Com Keys. The one selected for this example isbased on combinations available from multi-integer vectors. A 20 integervector has a total of 20! (20 factorial) combinations, i.e. 2.4329×10¹⁸unique arrangements, each of which can be used as a Com Key. Using theoriginal Com-Root time instant shared by any number of equipments, andmaking a new combination available from a pool of 20! at the rate of oneevery 10 nanoseconds, new Com Keys will then be available, withoutrepetition, for a period approximately 771 years. Increasing the ComRoot vector to 21 numbers will result in 5.1091×10¹⁹ unique combinationswhich will last for approximately 1,619 years available at the rate ofone every nanosecond. The availability, or generation rate, of Com Keysis of interest regarding the restriction of communications operatinglocations as will be explained later in this text.

The example in FIG. 19, explains the basic methodology employed in thisinvention, showing the signal transmission time relationship between aradio transmitter and receiver, 1901 and 1902 assuming directline-of-sight communication, with no multi-path signals. The data inputstream to the transmitter serves to modulate the RF signal, 1904, whichin turn is received and demodulated by the receiver, 1902, and appearsas data out, 1906. There is a finite time lapse between data in, 1903,and data out, 1906, comprised of the transmitter equipment processingdelay t_(e), 1907, the receiver equipment processing delay r_(e), 1908,both of which are assumed to be constants, for this example, and thefree space radio wave transit delay p, 1905, which is a function of thedistance separating the transmitter and receiver. In this case using aline-of-sight radio link, the direct signal path, assuming no refractionor other path altering phenomena, will be approximately direct via theshortest geometrical route from transmitter antenna, 1909, to receiverantenna 1910. The radio waves will travel at approximately the speed oflight, 3×10⁸ meters per second, so the free space delay, inmicroseconds, will be the distance in meters divided by 300. Thus, ifthe two equipment antennas are 1500 meters apart, the free space delaywill be 5 microseconds. In this example, for a specific data symboltransition at the data input, 1903, the total delay occurring prior tothe equivalent symbol transition appearing in the data stream, 1906, atthe output of the receiver will be the sum of the two equipmentprocessing delays, 1907 and 1908, and the free space transit delay,1905:t _(e) +r _(e) +p.

The following example explains the principle employed in one method ofestablishing a Com-Key. With reference to FIG. 20, a time instant isidentified for establishment of the Com Key, for Transmitter-1, 2001, byselecting a specific data symbol transition within a group of symbols asit transits a predetermined point within the transmitter. The signal,2007, is transmitted to Receiver-2, 2003 and the time of arrival of theselected symbol transition is identified, stored by the receiver andused as the basis for calculation of the algorithm coefficients fordecoding the masked signal received from Transmitter-1. The symbolstream, Data-2 Out, 2009, is looped back, 2010, via Data-2 In, 2011,Transmitter-2, 2004 and signal 2013, to Receiver-1, 2002, where theselected symbol transition is identified once more and matched to asecond accurate instant in time. The symbol round trip delay is thencalculated. It is assumed, for this example, that the Transmitter-1equipment delay, t_(e1), 2006, and Transmitter-2 equipment delay,t_(e2), 2012, are equal, similarly Receiver-1 equipment delay, r_(e1),2014, is equal to Receiver-2 equipment delay r_(e2), 2008. It is furtherassumed, for this example, that the go and return free space signaldelays, 2007 and 2013, are also equal. In this case the total round tripdelay is:d _(tot) =t _(e1) +p ₁ +r _(e2) +t _(e2) +p ₂ +r _(e1)

The link delay, d_(link), i.e. symbol transit time Data-1 In to Data-2Out, is then:d _(link)=((p ₁ +p ₂)/2)−(t _(e1) +r _(e2) +t _(e2) +r _(e1))/2=d_(tot)/2

The symbol transit time d_(link) is calculated, stored and used byTransmitter-1 as an offset time value to be added to the Com Key timeinstant identified, when calculating the algorithm coefficients fortransmission for communication with Receiver-2. For example, ifd_(link)=5 μS and the common operating time base interval is μS, thenthe actual time instant used for the Com-Key to generate the waveformcoefficients for transmission from Transmitter-1, 2001, to Receiver-2,2003, will be the instant occurring 5 μS later. The time instantreceived and stored by Receiver-2, 2003, in the loop-back procedure isused directly as the Com-Key to generate the necessary waveformcoefficients to enable communication. The same Com-Key can then be usedfor communication in both directions, i.e. from Transmitter-1, 2001, toReceiver-2, 2003, and in the other direction from Transmitter-2, 2004,to Receiver-1, 2002. Separate Com-Keys can be generated forcommunication in each direction, by repeating the loop-back procedure,starting this time with Transmitter-2, 2004, and looping back viaReceiver-1, 2002, and Transmitter-1, 2001. This will provide increasedsecurity.

FIG. 21 shows a flow chart of the Com-Key establishment described in theforegoing example. The selection of the Com-Key time instant, 2101, andthe symbol transition transmission, 2103, are simultaneous events.Storing the time instant, 2102, is not in itself a time sensitive event.Receiver-2 receives the transition, 2104, contained in the sequence ofsynchronization symbols and as it passes a predetermined point in thereceiver processing, the time of occurrence is noted and stored, 2105.This time instant then becomes the Com-Key, 2106, from which thewaveform coefficients are created, 2107. The symbol group containing thetransition is looped back, 2108, via Transmitter-2 and received byReceiver-2, 2109. As the symbol transition passes a specific point inthe receiver process, the time-of-arrival (TOA) is determined, stored2110, and used to calculate the link delay, d_(link) 2111. A new timeinstant at Com-Key time instant, 2101 plus the delay d_(link) iscreated, 2112. The Com-Key is now used to create the necessary waveformcoefficients, 2113, and 2114. Because of this offset delaying the finalCom-Key time instant by the exact amount of the cumulative transmissiondelay, both Transmitter-1 and Receiver-2 have identified and may now usethe identical time instant as the Com-Key for communication, 2115. Thesame Com-Key may be used for communication in the reverse direction, asdescribed above.

A further example follows of a method of setting Com Keys from one endof the link only, wherein the signal is not looped back. In accordancewith FIG. 22, all time is divided into finite periods, commencing at theCom-Root instant shared by all communicants. In this example, time isdivided into 100 microsecond (μS) periods. Each 100 microsecond point intime, 2201, 2202 and 2203, is a Cardinal Timing Point (CTP). The timebetween CTP's is divided into divided again into Ordinal Timing Points(OTP), 1 uS increments in this example. The division of time andsubsequent CTP's may be changed to fit the parameters of thecommunications system and links therein. In this example, a CTP isidentified for establishment of a Com-Key for the station initiatingcommunication and the OTP period of 1 uS is used for Com Key timingestablishment. The specific data symbol transition, within a group ofsymbols used for synchronization, as previously described, is selectedto be coincident with a CTP. The transmission containing thesynchronization symbol will be received at the other end of the radiolink and the time of receipt accurately recorded. The time of receiptwill be later than the time of transmission by the sum of the amount ofthe free space signal transit delay plus the processing delays of boththe transmitter and the receiver, as described in detail in theforegoing. Providing the total delay is less than 99 uS, the timeinterval between the time-of arrival and the next CTP can be measured bythe receiver to permit calculation of the exact time of transmission. InFIG. 22, CTP 2202, is used for Com-Key origination and hence the time ofemission. The signal is received at OTP 2208, 63 uS later by the distantstation, 2206. The receiver continuously counts the OTP's between CTP's,thus would immediately recognize that the transmission delay was equalto 63 μS. If the receiver is not programmed to continuously count theOTP's between CTP's, the receiver immediately counts 37 uS 2207, to thenext CPT 2203 and subtracts the count from 100 to establish thattransmission was made at CTP 2202, 63 uS prior to receipt. The receiveand transmit Com-Keys are established to coincide with CTP 2202, at bothstations. The transmit and receive timing at the originating end of thelink are time synchronized to timing at CTP 2202, and work in real time.Both the receive and transmit timing at the distant station 2206, arenegatively offset by 63 uS so that communications in either directionwill synchronize. If either or both stations are mobile, relocation willbe dynamically compensated by either station by timing offsets, asdescribed later in this document. There are numerous other methods ofCom-Key synchronization which will now become apparent, from theforegoing explanation, to those well versed in the art.

If the actual path between the two units is either a reflective orrefractive path or other than direct, the electrical signal path lengthwill differ from the actual geographical separation. The calculationwill be completed in the same manner as before, as the relativedistance, i.e. the actual signal path length is the measurement used toestablish the transmission algorithm coefficients. By this method,indirect communications connections can be established using multiplesub-links via relay stations, satellite communication, physicalconnections or other means. In multi-hop connections, it is notnecessary for each sub-link to establish Com-Keys and associatedalgorithm coefficients, as the relay equipment may operate in atransparent manner, if desired, provided transit delays are constant.Conversely, it may be desirable to establish different Com-Keys forsome, or all elements in the end-to-end communications link, forsecurity or other reasons.

Master Timing Oscillator Drift

In cases where GPS or other accurate time synchronization source iseither unavailable or denied, equipment frequency control oscillatorsmay drift such that two or more equipments' time may not be reciprocallyrepresentative. In such cases, communication synchronization may beattained by use of a CTP, whereby the communication originatingequipment's current time-keeping is used for the time reference forsynchronization, albeit inaccurate. The essential, when synchronizingfor communication, is not accurate time-keeping, in itself, but theability of both equipments to identify an instant in time and agree toidentify it as the same one, regardless of when that may occur.

The precision of a master timing oscillator is commonly specified interms of maximum frequency deviation in a 24 hour period:

$\delta = {\frac{\Delta\omega}{\omega_{0}}{{{Hertz}/{Hertz}}/{day}}}$

where: ω_(o)=nominal oscillator frequency

-   -   Δω=frequency deviation

In the absence of GPS or other accurate reference time signal, theoscillator can drift in accordance with the following expression showinga linear frequency drift. It should be noted, however, that thatoscillators do not necessarily continue to drift only in one direction.However, once the oscillator has initially stabilized after activation,frequency drift may be predominantly unidirectional.

$\begin{matrix}{{{\Delta\omega}(T)} = {{\omega_{0}{\int_{0}^{T}{\delta\ {\mathbb{d}t}}}} + {\Delta\;{t(0)}}}} \\{= {{\omega_{0}\delta\; T} + {{{\Delta\omega}(0)}\mspace{14mu}{Hertz}}}}\end{matrix}$

Time reference error for the same oscillator, on the other hand, maygrow quadratically:

$\begin{matrix}{{\Delta\;{t(T)}} = {{\int_{0}^{T}{\frac{\Delta\;{\omega(t)}}{\omega_{0}}\ {\mathbb{d}t}}} + {\Delta\;{t(0)}}}} \\{{= {{\int_{0}^{T}{{\delta t}\ {\mathbb{d}t}}} + {\int_{0}^{T}\frac{{\Delta\omega}(t)}{\omega_{0}}} + {\Delta\;{t(0)}}}}\ } \\{= {{\frac{1}{2}\delta\; T^{2}} + \frac{{{\Delta\omega}(0)}T}{\omega_{0}} + {\Delta\;{t(0)}}}}\end{matrix}$

As stated previously, it is necessary to calculate the maximumoscillator drift for any period lacking time reference intervention andto dimension the CTP accordingly. For example, this can be a firmwaresetting, a field programmable setting, or other, in an embodiment ofthis invention.

FIG. 23 shows an example of how a synchronization window may bedetermined for equipment operating in the absence of time-referencesynchronization. Time, 2301, is divided into 1 μS OTP's, 2305, in thisexample, in accordance with mutual operational timing, as described inthe foregoing. For communication synchronization of two or more units ofequipment in the absence of GPS or other time standard correctiveintervention, the maximum time deviations are calculated for all unitsfor the maximum period of accurate time synchronization denial. Themaximum absolute value of deviation calculated is then used to dimensionboth positive and negative drift limits, 2306, 2307. A drift value of499 μS is used in this example. This value, 499 μS is set for bothpositive and negative drift limits, 2306 and 2307, as preciously stated,as the timing oscillators may drift either positively or negatively.Therefore, if any two oscillators drift in opposite directions, themaximum drift must be applied to embrace the extreme directional driftpossibilities of both oscillators. The sync window, 2308, is therefore:2×absolute maximum drift+2, in OTP units. Insomuch as compensatorytiming offsets may be used by communicants instead of direct unitsynchronization, in the presence of oscillator drift, it is necessary toallow for elapsed time in respect of TOA transmission signal delays. Toallow for this, CTP's should be placed other than at the drift limits+1,i.e. at the sync window limits, 2308. In this example, CTP's, 2302, 2303and 2304, have been placed at twice the sync window limits.

A further flow chart showing the basic principle of initializationtaking master timing oscillator drift is shown in FIG. 24. The equipmentunits that will communicate with each other are connected, 2401, to aninitialization controller, or other means, which steps the units througheach phase of initialization in concert. The connection setup is suchthat all delays between the controller and the equipment response tocommands are either the same or compensated for in all units withinlimits that will ensure that the same time instant is detected andstored by all. The lowest master clock rate, or other limiting timingfactor is determined for the units, 2402. This will be the limitingfactor to determine the smallest time interval at which new waveformcoefficient keys, Com-Keys, may be generated for mutual operation. Themaster clock rate and, or other information for determining the keygeneration interval, may be obtained in a number of different ways, suchas, but not limited to: they may be stored in equipment firmware,derived algorithmically or entered manually, for example. The maximumdrift, 2403, for all equipment is calculated as explained in theforegoing. The data on which these calculations are based may be storedin firmware, as an integral part of the equipment operating system,entered manually or communicated to the equipment and or controller, byother means. The drift limits and synchronization window to be used byall units is determined and set up in all units, 2404. All units accessGPS, or other time standard, and synchronize, 2405. Following timesynchronization of all units, a set of initialization data symbols isassembled by the controller within which a specific transition will beused by all to set the Com-Root. The controller then transmits thesymbol sequence to all units simultaneously. All units will acquire thetransition at the same time and register this and record the precisetime-of-day as the Com-Root, 2406. As the controller did notpredetermine the time instant, the Com-Root generation is truly randomand anonymous. Based on the lowest master clock rate, 2402, all timefollowing the Com-Root instant will be divided into OTP's, 2407. Themaximum range or distance between any two communicants is entered intothe controller, 2408. This may be direct line-of-sight or other indirectdistance, including, but not limited to reflective, refractive,multi-hop, satellite or other. The object is to ascertain the TOA delayso that CTP's can be set to take all delays into account. Wheresignificantly different delays are to be encountered, more than one typeof CTP's may be used as will be more fully explained, later in thisfiling. The CTP's are set, 2409, in accordance with the foregoing clockdrift and sync window example, where extreme range or distances are notanticipated. All units are now disconnected, 2410, and continue to trackelapsed time, 2411.

In cases where GPS or other accurate time synchronization source iseither unavailable or denied, equipment frequency control oscillatorsmay drift such that two or more equipments time may not be reciprocallyrepresentative. In such cases, communication synchronization may beattained by use of a CPT. The communication originating equipmentcurrent time-keeping is used as the immediate time reference forsynchronization. Time correction may be made at a later time, using oneor the other equipment, or independently, where both equipments have GPSor other time reference access.

In a similar manner to that described previously, in accordance withFIG. 20, a time instant is identified for establishment of a Com Key,for Transmitter-1, 2001, by selecting a specific data symbol transitionwithin a group of symbols as it transits a predetermined point withinthe transmitter. On this occasion, the time instant selected iscoincident with a CTP. The signal, 2007, is transmitted to Receiver-2,2003 and the time of arrival of the selected symbol transition isidentified and stored as a preliminary point to CTP timesynchronization; an initial timing adjustment, in that respect, is madeby Receiver-2. This interim timing adjustment will now set Receiver-2timing to lag Transmitter-1 timing by the amount of the transit delay.The signal from Transmitter-1 is looped back via Transmitter-2 toReceiver-1, as previously described. The time delay from Data-1 In toData-2 Out is calculated as previously detailed. A second group ofsymbols is transmitted, by Transmitter-1, containing a symbol transitioncoincident with a second CTP, followed by a second symbol transitionseparated from the first by the amount of the calculated TOA delay.Receiver-2 corrects its timing by advancing it to reflect the Data-1 Into Data-2 Out TOA delay. Transmitter-1 uses this second transition asthe Com-Key as Transmitter-1 and Receiver-2 now have synchronized timereferences. Receiver-2 then uses the second transition in the lattertransmission as the Com-Key.

The timing provided by the foregoing synchronization procedure, whileallowing equipment and system synchronization, may not be accurate inrespect of the GPS derived timing whereby the Com-Root was established.Timing synchronization of this nature is sufficient to establish andconduct communications on a temporary basis in the absence of anaccurate time reference. When an accurate time reference such as GPS isavailable to all communicating stations, it is then possible tore-establish accurate station timing individually by direct reception ofthe GPS, or other, timing signal and then perform timing correction andresynchronization in concert in accordance with an operational protocol.

When, however, GPS or other reference signal is not available to allcommunicants, timing correction may undertaken initially by one stationhaving access to GPS, or other reference signal, direct access to allother communicants, using a CTP plus a second transition relative to thedelay associated with each station, as described in the beginning ofthis section. Where the station with access to GPS or other referencesignal is not in direct communication with all other stations, timecorrection may be undertaken sequentially by correcting a station andusing it to correct the timing of other stations with which it is incommunication. Timing corrections made by indirect means, as describedin the foregoing are logged by the corrected equipment, so that accuratetiming can be restored when direct access to a reference signal isavailable.

Another method of synchronization for communication using a CTP in thecase of drifted oscillators, is as follows. The originating equipmenttransmits the synchronizing data-symbol sequence with thesynchronization transition coincident with a CTP in its current timing.With reference to FIG. 23, the CTP, 2303, will always be within its syncwindow, 2308, but offset from a central position, in accordance with theamount of drift sustained. The receiving communicant will see thetransition as the CTP present within its sync window, albeit notcoincident with the CTP positioned by its current time-keeping. Becausethe drift limits, 2306 and 2307, have been set to embrace the extremes,a CTP representing the same time instant will be seen by both unitswithin the limits of the sync window, in all cases, though notcoincidentally, in the case of drifted time keeping. The transition timeinstant will be marked and stored by the receiving equipment, which willthen temporarily adjust its timing for the duration of thecommunication. Both equipments will then either use the CTP time instantto create Com-Keys for communication, as described in the foregoing, orperform further synchronization, as previously described to measure TOAdelays and create other Com-Keys. At the cessation of communications,the equipment will return its time keeping to its original state, toremove any additive error, so that the sync window, 2308, with the driftlimits, 2306 and 2307, will remain valid for future communicationsessions. It will be recognized from the foregoing examples, by thoseskilled in the art, that when using CTP synchronization, further finesynchronization at the OTP level will be necessary to restrict theoperational area of Com-Keys as described later in this document.

The following describes one method of synchronization and generation ofvalid Com-Keys for communication, in cases where equipment has beencompletely shut down, such that there has been complete discontinuity ininternal time keeping rendering elapsed time interval data unavailable.Super cardinal time points (SCTP), are used to enable manual systementry. SCTP's are set in the same manner as CTP's, except that theelapsed time between them is much greater. For example, for manualreactivation, the SCTP's may be 5, 10, 15 minutes apart, or have evengreater separation to sufficiently account for personal time keepinginaccuracies. Smaller divisions may be used such as a few seconds to 2or 3 minutes where current time is directly obtained from a computer, orother device, with time keeping capability. In all cases it will benecessary to convert any time used to an agreed time zone orinternational time, i.e. Greenwich Mean Time (GMT) as a common base. Theoperation of SCTP's is similar to that of CTP's, providing initialsynchronization between unit sufficient to generate valid Com-Keys andperform secondary fine synchronization at the OTP level to limit areasof operation, as described in the following section.

Because of the random selection of the Com-Root instant, all timekeeping instants after that are equally random, in relative time. Timekeeping, with added oscillator drift inaccuracies, while reflecting agross drift error, will still retain the OTC accuracy for inter-unitcommunication, when synchronized, as described in the foregoing or byany other method derived from this methodology.

Restricted Reception and Key Validity

The omni-directional emitter, 2501, in FIG. 25 transmits the radiosignal in all directions such that the radio waves traveling atapproximately 3×10⁸ meters per second will cross each of the concentriccircles, 2502, spaced equi-distantly 300 meters apart, at intervals of 1μS. The signal, 2504, will transit the space bounded by 2503, in aperiod of 1 μS. Similarly, the signal 2506, will enter the space boundedby the circles 2503 and 2507, after 1 μS and exit after 2 μS, the intercircle transit time being 1 μS. Therefore, if unique Com-Keys referencedto the specific Com-Root instant in time are permitted to be generatedat intervals of 1 μS, then a particular Com-Key generated for a receiverlocated, say 1300 meters from the emitter, 2501, within the area boundedby the concentric rings, 2509 and 2510, at 1200 and 1500 metersrespectively, will be valid for the signal received by that receiver fora distance of 1300 meters+200 and −100 meters. Because the Com-Keyagainst which the signal is coded for transmission is based on onespecific instant in time and the Com-Key used by the distant receiver isbased on the same time instant, delayed relative to the originaltransmit instant to compensate for the signal delayed TOA, the Com-Keyrelationship will only be valid for 300 meters following the distancerepresented by the time offset. As the receiver moves out of the 300meter validity area, the receiver algorithm timing will no longercoincide with that of the transmitted signal, thus the transmitter anddistant receiver will no longer synchronize.

FIG. 26 is a linear representation of areas of Com-Key validity, 2603,as a function of distance, 2601 and time, 2602, for Com-Keys generatedat one microsecond intervals. Different magnitudes of validity can beestablished by use of various Com-Key generation intervals, e.g.Com-Keys generated at the rate of one every 10 nanoseconds will reducethe concentric circle separation, hence the location validity to 3meters, conversely, Com Keys generated at the rate of one every 10microseconds will increase the area of valid operation to 3 Kilometers.The round trip delay signal transit delay, 2604, 2605 and 2606, (seeFIG. 20, Data-1-In 2005, to Data-1-Out, 2015) are all reiterated forconvenience.

Network Embodiment Examples

One example of an embodiment of this invention in FIG. 27 shows aninfrastructure type network comprising a base station, or access point,2701, with remote stations, mobile or fixed, 2702-2706. The station,2702, is separated from the base station, 2701, by the distance, 2711.This distance is the signal path, electrical distance, which may bedirect line-of-sight, or indirect via other route. In this example, weshall assume that all the remote stations are mobile units. Each of theunits establishes a Com-Key for communication with and via the basestation, 2701. The time and distance relationship between the twoentities will result in a defined physical area of operability for eachmobile. If the central station, 2701 communicates with all mobiles usingan omni-directional antenna, the area of operability associated witheach Com-Key will be approximately circular, as described in theforegoing. However, the use of directional and or smart antennas willimpose additional limitations on specific areas of operability. For thisexample, the signal emission pattern from the central station, 2701, iscircular. Also, in the example, mobile, 2702, is located at a distance,2711, from the base station and assuming that the Com-Key for thatcommunications link was generated on the basis of one per microsecond,the resulting 300 meter operating area, 2708, will be held at adistance, 2707. Similarly, a valid operating area, 2709, will beestablished for remote station 2703, at a distance, 2710. Conversely, itwill be seen, therefore, in both cases, the base station will be locatedin a valid operating area specific to communication with each mobile,2702 and 2703. The latter valid operating areas are not shown in FIG.27, for the sake of clarity.

When the Com-Keys are set by stations, 2701 and 2702, each station willoffset the timing of the transmit algorithm to time-distancerelationship with the other, such that the communicating receivers mayuse a real-time instant for the receive Com Key, as previouslyexplained. In this example where the remote stations are assumed to bemobile units, it may be necessary from time-to-time to reposition thearea of valid operability, when the units move nearer or further awayfrom the base station. Lateral movement will have no effect, in thisexample, provided the resulting longitudinal distance from the basestation does not vary more than that permitted by the establishedoperability area. However, in accordance with FIG. 27, if longitudinalmovement exceeds the limits of the valid operating zone and no timingcompensation is made, the current Com-Key will become invalid, becauseof delayed time-of-arrival of the signal at the receiver. In this event,the receiver will lose synchronism with the transmitter and will nolonger be able to acquire the signal and retrieve the information.Similarly, the base station will no longer be able to receive signalsfrom the mobile.

FIG. 28 shows an example of an arrangement whereby the mobile stationsare able to move freely and adjust the Com Keys to compensate fordeviations from the initial set-up location. The received signal, 2801,is connected to three or more window detectors, five are shown in theexample, 2802-2806. The reference signal, 2807, based on thecoefficients provided by the Com-Key and synchronized timing currentlyin use to the correlator detector 2802. The same reference signal isprovided to the other four correlators, 2803-2806, with timingincrementally advanced or retarded from current synchronization viareference signal timing controllers, 2810-2813. Advanced timing isprovided by controller, 2810, and further advanced timing is provided bycontroller, 2812. Retarded timing is provided in similar increments bycontrollers, 2811, and 2813. The degree of offset timing applied to thesignal by each detector would normally depend on the rapidity andfrequency of signal time-of-arrival variation experienced or expected ina dynamic system deployment of the technology. For example, aspreviously explained, if the Com-Keys used for the current example weregenerated on a one per microsecond basis, thereby relating to possiblelocation deviations of +/−150 meters, the timing offsets used inconjunction with detectors 2803-2806 may be set to differ incrementallyby same amount, or controllers, 2810, and 2811, may have lesserincremental deviation from current synchronization timing, thancontrollers, 2812, and 2813, so that fine tuning may be achieved. As theposition of the mobile changes, or other causes result in differingsignal time-of-arrival, the correlators, 2803 and 2804, adjacent to thecurrent timing correlator, 2802, will initially detect the change,followed by the outer correlators, 2805, and 2806, except where aninstantaneous change of signal path occurs, in which case the latter maydetect the change first. The decision element, 2814, of the sub-systemin FIG. 28, selects the input from the correlators, 2802-2806 with thebest correlation and feeds the information back to the timingcontroller, 2808. The timing is adjusted as necessary to optimizesynchronization with correlator, 2802, whilst retaining signal trackingwindow provided by correlators, 2803-2806 By this manner, a correctlysynchronized signal will always be present at the output 2815. A numberof variations of this example are possible rendering various advantagesaccording to the operating conditions encountered including, but notlimited to, RAKE receivers, open loop synchronization, closed loopsynchronization, matched filter bank estimation, etc. Such variations,realized in either software or hardware, may easily be employed in adynamically adaptable embodiment of the present invention.

In a system, such as the one depicted in FIG. 27, where there are anumber of remote mobile stations communicating via a central basestation, it will be unnecessarily burdensome for the base station tocontinuously track and adjust the Com-Key timing associated with eachmobile, although in some circumstances this may be desirable. Themobiles may offset all link timing in both directions, while the basestation retains the status quo, in order to keep both mobile and basestation Com-Keys operable, regardless of mobile movement and location.

With reference to FIG. 27, in a further example of a network where thereare a number of remote mobile stations communicating via a central basestation, a single Com-Key may be used for communications with allstations in both directions. In this example, the network utilizespacket communication protocol, such as, but not limited to, InternetProtocol (IP) or ETHERNET. The mobile units, 2702-2706, communicate withthe central station, 2701, in short RF bursts, containing a number ofinformation packets. Each packet, in accordance with commonly usedcommonly used communications practices, would be addressed to thecentral station, 2701, at the appropriate protocol level. Thus, eventhough certain mobiles may be physically located in the same Com-Keyoperational zone, (reference FIG. 25), and decode and demodulate thecarrier, the packet(s) would be ignored, in accordance with theaddressing protocol. Similarly the, the central station, 2701, using thesame Com-Key in the reverse direction, transmits a signal which isreceived by all mobiles, 2702-2706, which have automatically adjustedtheir Com-Key timing to achieve synchronization in accordance with theirindividual locations relative to the central station. The signal isreceived by all mobiles, the waveform demodulated and the individualpackets disregarded by all but the addressee. Conversely, by thismethod, the central station can effect an “all call” communication withpackets bearing the addresses of all mobiles which will simultaneouslyreceive the entire communication.

It will readily be seen, by this method, that conference calls may bemade involving part, or all network units, whereby the mobiletransmitted packets are relayed to all other mobiles by the centralstation. Furthermore, those versed in the art will see that that as eachcommunicant drops from a conference call, or disconnects from thenetwork, it is possible to automatically change Com-Keys for remainingcommunicants, thus providing increased security.

Ad-Hoc Networks

The technology resulting from the present invention can also be used toadvantage in ad-hoc networks and other more complex arrangements of thistype, as shown in one example of an embodiment in FIG. 29. Fivestations, 2901-2905, are all able to communicate directly with eachother, using individual Com-Keys. Each communication link Com-Key willcreate a restricted area of operation for each individual user. Station,2901, in communication with station, 2902, via link, 2906, will createlongitudinal areas of operation within the limits 2907 an 2908, forstations 2901 and 2902 respectively. Any movement of the station whichwould render the Com Key timing inoperable will be offset by the stationin motion, as previously explained. Links with other stations in thenetwork will create similar Com-Key link limitations which must betracked and dynamically offset the timing to update location relatedoperability.

With reference to the foregoing infrastructure network examples, it willbe apparent to those skilled in the art, that, press-to-talk (PTT)networks may also be operated, using a single Com-Key, common to allunits, for communication in both directions. In this example, it isnecessary for each mobile to temporarily store the timing offset forCom-Key operation for each of the other mobiles. As a particular mobiletransmits, all other mobiles automatically select the necessary Com-Keytiming offset, relative to location, to demodulate the waveform. Asanother mobile presses-to-talk, all listening mobiles will select theappropriate Com-Key timing offset to receive and demodulate thewaveform.

Furthermore it will also be apparent that simplex, semi-duplex andcontention type networks, including IEEE Standard 802.11 communicationswill also work with the technology, described in connection with thisinvention. The equipment delays will now include additional protocoldelays, which can be predetermined and included in the total delaycalculations.

Relative Location of Stations

The time-distance relationship that exists between stations as a resultof the radio wave transit time between transmitting and receivingantennas, time of arrival (TOA) is used for dynamic relative stationlocation determination. In a simple two station radio link withunobstructed line-of-sight communication, the most direct path taken bythe signal, usually resulting in the strongest received signal, will beapproximately: distance in meters=elapsed time in microseconds×300. Asdescribed in the foregoing, any movement of one or both of the stationswhich either lengthens or shortens the transmission path between thestations will result in a change in signal transit time, thus providinginformation to calculate a new distance between stations, though if notnecessarily sufficient in itself, under most circumstances, to calculateeither direction of movement or new relative coordinates. However, witha minimum of four stations, the cumulative information providessufficient data to calculate both distance and direction of movement;thus providing the relative location of all stations to one another. Ina further example with reference to FIG. 29, assuming for the sake ofsimplicity that the network stations all have unobstructed line-of-sightcommunication with one another. Once communication has been establishedbetween all stations, information is available to facilitate calculationof the distances between them, the azimuth relative to each other,direction and rate of movement, from the free-space transit times overeach path and application of elementary trigonometry. Furthermore, ifthe coordinates of one of the stations is known, the locations of theothers may easily be calculated by the same methodology. Relativelocation, velocity and direction of movement of communicants in anetwork can be continuously updated automatically by a simple residentprogram as part of the equipment operating system.

As described in the foregoing, the degree of definition of the distancemeasurements, hence location, direction and velocity is directly relatedto the degree of timing refinement available in the equipment. Whilemicrosecond accuracy may be the highest available for Com-Root andCom-Key purposes, because of oscillator drift contribution to cumulativetime inaccuracy, timing inaccuracies incurred for TOA measurements arenon-cumulative and instantaneous relative only to the very briefmeasurement time period itself. These timing errors can therefore beignored. Thus higher frequencies, either the fundamental of a muchhigher frequency master clock oscillator, or a harmonic of the masteroscillator. A timing frequency with a period of 10 nanoseconds willenable positioning measurements of +/−1.5 meters, for example and ifboth the rising and falling edges of the clock signal are used, themeasurement refinement is doubled to +/−75 centimeters.

It will be readily apparent to those skilled in the art that the samerules for position and distance determination will apply to networkswith other numbers of stations and topologies. As mentioned earlier, GPStiming signals may be used for accurate timing synchronization fromtime-to-time, similarly, position coordinates may be initially obtainedfrom GPS and subsequent changes of station location and coordinates ofnew stations joining the network may be calculated as described. It willalso be seen that the absence of GPS, either temporarily or permanently,will not affect the relative positioning, velocity and directioncalculation capability of this invention. The ability of this inventionto fully function with commercial or relatively low stabilityoscillators in the absence of an accurate time reference in an ad-hoc orinfrastructure type modes differentiates it from all prior art. It willalso be readily apparent to those skilled in the art, that distances,velocities, directions and coordinates of stations communicating viaindirect or multi-link radio paths can be extrapolated from theforegoing with the aid of calculated correction factors applicable tothe network parameters and circumstances. The latter extrapolations canbe made to include, amongst others, refractive, reflective, fading,Doppler influenced and multi-link signal paths.

While I have described in the foregoing the principles of my inventionin connection with specific apparatus, it is to be clearly understoodthat this description is made only by way of example and not as alimitation to the scope of my invention as set forth in the objectsthereof and in the accompanying claims.

1. A method of reducing deterministic and cyclostationary features of adirect sequence spread spectrum (DS-SS) transmit signal, comprising:generating at a transmitter a plurality of independent, unrelated randomstochastic sequences with independent distributions; generating at thetransmitter a DS-SS transmit signal having a plurality of waveformparameters that are independently varied over time in respectiveaccordance with the plurality of independent, unrelated randomstochastic sequences, wherein the plurality of waveform parameters thatare varied includes at least two of: RF carrier frequency, RF carrierfrequency dwell period, data symbol rate, data symbol rate dwell period,chip clock frequency, chip clock frequency dwell period, and a one-timeuse pseudonoise (PN) spreading sequence; and transmitting the DS-SStransmit signal.
 2. The method of claim 1, wherein the plurality ofwaveform parameters includes the one-time use PN spreading sequence,which is longer than a given communication period.
 3. The method ofclaim 1, wherein the waveform parameters are varied such that the PNspreading sequence is generated with an integer number of chips per datasymbol.
 4. The method of claim 1, wherein the waveform parameters arevaried such that the PN spreading sequence is generated with anon-integer number of chips per data symbol.
 5. The method of claim 1,wherein the plurality of waveform parameters includes the chip clockfrequency and the chip clock frequency dwell period, wherein the chipclock frequency and the chip clock frequency dwell period are variedindependently.
 6. The method of claim 5, wherein the plurality ofwaveform parameters further includes chip clock phase.
 7. The method ofclaim 6, wherein varying the chip clock frequency, the chip clockfrequency dwell period, and the chip clock phase coincides with datasymbol transition timing.
 8. The method of claim 6, wherein varying thechip clock frequency, the chip clock frequency dwell period, and thechip clock phase does not coincide with data symbol transition timing.9. The method of claim 1, wherein the plurality of waveform parametersincludes the data symbol rate.
 10. The method of claim 9, wherein theplurality of waveform parameters includes the data symbol rate dwellperiod.
 11. The method of claim 1, wherein the plurality of waveformparameters includes the RF carrier frequency.
 12. The method of claim11, wherein the plurality of waveform parameters includes the RF carrierfrequency dwell period.
 13. The method of claim 1, wherein the pluralityof waveform parameters includes RF carrier amplitude.
 14. Acommunications device capable of reducing deterministic andcyclostationary features of a direct sequence spread spectrum (DS-SS)transmit signal, comprising: a controller configured to generate aplurality of independent, unrelated random stochastic sequences withindependent distributions; and a transmitter configured to generate aDS-SS transmit signal having a plurality of waveform parameters that areindependently varied over time in respective accordance with theplurality of independent, unrelated random stochastic sequences, whereinthe plurality of waveform parameters that are varied includes at leasttwo of: RF carrier frequency, RF carrier frequency dwell period, datasymbol rate, data symbol rate dwell period, chip clock frequency, chipclock frequency dwell period, and a one-time use pseudonoise (PN)spreading sequence.
 15. The communications device of claim 14, whereinthe plurality of waveform parameters includes the chip clock frequencyand the chip clock frequency dwell period, and wherein the transmitteris configured to independently vary the chip clock frequency and thechip clock frequency dwell period.
 16. The communications device ofclaim 14, wherein the plurality of waveform parameters includes the RFcarrier frequency and the RF carrier frequency dwell period.
 17. Acontroller readable non-transitory medium encoded with instructionsthat, when executed by a controller, cause the controller to: generate aplurality of independent, unrelated random stochastic sequences withindependent distributions; generate a DS-SS transmit signal having aplurality of waveform parameters that are independently varied over timein respective accordance with the plurality of independent, unrelatedrandom stochastic sequences, wherein the plurality of waveformparameters that are varied includes at least two of: RF carrierfrequency, RF carrier frequency dwell period, data symbol rate, datasymbol rate dwell period, chip clock frequency, chip clock frequencydwell period, and a one-time use pseudonoise (PN) spreading sequence.18. The controller readable non-transitory medium of claim 17, whereinthe instructions that generate the control sequence compriseinstructions that cause the controller to independently vary the chipclock frequency and the chip clock frequency dwell period.
 19. Thecontroller readable non-transitory medium of claim 17, further encodedwith instructions that, when executed by the controller, cause thecontroller to independently vary the RF carrier frequency and the RFcarrier frequency dwell period.